1. Field of the Invention
The present invention relates to a wire bonding apparatus and more particularly to a wire bonding apparatus that includes a light path conversion means which directs an image of the area near the lower end of a bonding tool to a position detection camera.
2. Prior Art
A typical wire bonding apparatus includes a bonding tool (merely called xe2x80x9ctoolxe2x80x9d) which performs bonding on a bonding part, a position detection camera which has a lens barrel and images the bonding part, and a light path conversion means which directs an image of the area near the lower end of the tool to the lens barrel. Japanese Patent Application Laid-Open (Kokai) No. 2001-203234, for instance, discloses a wire bonding apparatus as described above. Though not described in this prior art, illuminating light is emitted downward through the lens barrel so that the position detection camera can acquire a clear image of the bonding part.
In the above structure, if an image of the tool or an image of the tool and a reference member is acquired while the light source on the lens barrel side is lit, the illumination of the light source will be reflected by the tool or the reference member, and the overall contrast drops, thus causing a deterioration in the image that is acquired. Such an image tends to contain an element of error when image processing is performed. Such effects of the light source can be eliminated by switching off the light source or by lowering the light quantity.
When investigating the bending of the wire (tail) that extends from the lower end of the tool, the tail length or the diameter of the ball that is formed by melting the wire tail, it is important that the results be immediately fed back to a controlling section. Accordingly, switching off of the light source hinders the productivity and is therefore undesirable. In cases where a halogen light source which is inexpensive and superior in terms of illumination intensity is used as the light source, switching the light source on and off is particularly undesirable. This is because the switching time of the illuminating light amount of halogen light source is generally slow.
The object of the present invention is to provide a wire bonding apparatus that includes a light path conversion means that causes no deterioration of the quality of acquired image even if the light source that provides illumination from the lens barrel of the position detection camera is lit.
The above object is accomplished by a unique structure of the present invention for a wire bonding apparatus that includes: a tool that performs bonding on a bonding part, a position detection camera which has a lens barrel and images the bonding part, a light source which emits illuminating light downward through the lens barrel, and a light path conversion means which directs an image of an area near the lower end of the tool to the lens barrel; and in the present invention, a wavelength-selective filter is provided in the light path conversion means so as to be within a light path of the image of the area near the lower end of the tool, the wavelength-selective filter allowing illuminating light of the light path conversion means to pass therethrough and prevents illuminating light from the lens barrel side from passing therethrough.
In the above structure, the wavelength-selective filter is disposed above a reflective member which is provided in the light path conversion means and reflects the image of the area near the lower end of the tool upward.
Instead, the wavelength-selective filter can be disposed on an image-light incident side of the reflective member.
In addition, in the present invention, the wavelength-selective filter is disposed so as to incline at an angle that is greater than numerical aperture of the lens barrel of the position detection camera.